1- Diagnosis of some ectoparasitic diseases as mite, lice, tick, fleas and filariasis
2- Diagnosis of some mycotic diseases as Ring worm (Dermatophytosis – Dermatomycosis)
3- Diagnosis of some bacterial diseases as dermatophilosis (Moist exudative dermatitis)
4- Diagnosis of some viral diseases (Pox, ORF and LSD)
Definition: Chronic contagious diseases of all animals and human transmitted by direct and indirect contact and characterized by macule, papule, vesicle, pustule and scab
A) Field diagnosis:
1- Case history: ask about a- Previous case of infection in the herd b- Previous treatment of mange in herd c- History of introduction of new animal d- Cleaning and disinfection program
2- Clinical signs and PM: a- Presence of irregular areas of alopecia with sever itching and pruritus of skin b- Thickening and folding of skin c- Poor general animal condition d- Rough coat and skin erythema
B) Lab diagnosis:
Sample: Skin scraps (Sample must be collected from periphery of the lesion or edges until blood oozing using sharp scalpel)
Touch skin by mineral oil or dip scalpel in oil or glycerin to avoid cuts in skin
Hold fold of skin between healthy and affected part, then scraping the crusts of fold by the sharp scalpel in one direction to avoid destruction of etiological agents till blood oozing.
Collect skin scraps in sterile petri dish then make:
1) Direct microscopic examination:
Put skin scraps on clean dry glass slide then add few drops of KOH or NaOH 10% to dissolve greasy materials and nitrogenous substances
Then examine under microscope "10x" to detect mite movement
2) Heat (Sedimentation) (Heat Sedimentation test)
Put skin scraps in clean dry test tube then add 10ml KOH or NaOH 10%
Gentle heating not boiling for 3:5 minutes to dissolve any nitrogenous material
Discard supernatant and examine 1 drop of sediment on glass slide under microscope
"10x" to detect presence of mite
Definition: Highly contagious infectious disease of all animals and human caused by fungi
(Trichophyton – Microscporum)

A) Field Diagnosis:
1- Case history: as Mange
2- Clinical Signs and PM: circumscribed area of alopecia covered by grayish white crust without itching nor pruritus of skin
B) Lab diagnosis:
Sample: Skin Scraps (Mackenzie brush technique)
Collected by brushing affected area of skin by sterile brush against paper sheet then put skin scraping in petri dish then make
1) Direct microscopic examination:
Put skin scraps on clean dry glass slide then add few drops of NaOH or KOH 10% to dissolve any greasy materials and nitrogenous substances or stained by blue lactophenol
Mild gentle heating then put cover slide then examine under microscope "10x" to detect arthrospores which present around hair follicles
2) Culture examination:
Need complete aseptic condition by washing affected area by soap and water then dry by filter paper then disinfection by alcohol 70%
Collect skin scraps by brushing affected area of skin by sterile brush against paper sheet then put skin scraping in petri dish
Inoculate skin scraps on surface of sabouraud dextrose media (SDA) containing:
1yeast extract as growth promoter for fungi
2- Chloramphenicol inhibit growth of bacteria
3- Cyclohexamide suppress growth of saprophytic fungi
Incubate at 37 ͦ C at pH 6.9for 5 days
Result:
Fungal growth +ve ring worm
Not discard
–ve plates before 5 weeks as trichphyton need 5 weeks to grow while microsporum need 5 days only to grow
Another media called Dermatophyte test meda (DTM)
Similar to SDA but contain phenol red (growth of white colored colonies with red color of surrounding media)
3) Wood's light
Used for diagnosis of Ring worm in long hair breeds of dog and cat
Introduce dog or cat into dark room or box then expose hair to UV light
Metabolites of fungus exposed to UV react with it producing yellow green fluorescent light indicate +ve ring worm